Electrographic transmitter



Oct. 6, 1959 R. PEEK, JR 2,907,824

ELECTROGRAPHIC TRANSMITTER Filed Oct. 23, 1957 IN VE N TOR R. L. PEEK,JR.

game M ATTORNEY United States Patent ELECTROGRAPHIC TRANSMITTER RobertLee Peek, Jr., New York, N.Y., assignor to Bell Telephone Laboratories,Incorporated, New York, N.Y., a corporation of New York ApplicationOctober 23, 1957, Serial No. 691,861

9 Claims. (Cl. 178-18) This invention relates to the electrographictransmis sion of images, and more particularly to a transmitter devicefor employment in an electrographic system.

Transmission system wherein graphic material is reproduced at areceiving station while being formed at a transmitting station are wellknown. Such systems commonly employ transmitter devices having stylusesto which electrical leads or rather involved mechanical linkages areconnected. These connections are frequently disadvantageous in that theyinterfere with the exercise of a natural writing style. Additionally,the mechanical or electrical intricacies of such apparatus are notadvantageous from a manufacturing or maintenance stand point. 7

An object of this invention is an improved electro" graphic transmitter.

More specifically, an object of the present invention is an improvedelectrographic transmitter which allows an operator thereof to exercisea completely natural writing style.

Another object of this invention is an easily manufactured and highlyreliable electrographic transmitter.

A still further object of the present invention is amagnetically-operated electrographic transmitter.

These and other objects of this invention are realized in anillustrative transmitter device wherein two crossed resistive windingsare positioned in parallel adjacent planes. Advantageously, only thebottom winding is of a magnetic material. Accordingly, when a permanentmagnet stylus is moved over the surface of the nonmagnetic or upperwinding, portions of the lower or magnetic winding are attracted intocontacting relationship with elements of the upper winding. 7

A switching device and a source of potential are included in thearrangement of the transmitter for alternately switching the source fromthe circuit of one winding to that of the other, thereby producingtransmitter output voltages proportional to the coordinates of positionof the stylus.

Accordingly, a feature of this invention is an electrographictransmitter comprising two crossed resistive windings arranged inparallel adjacent planes, one only of the windings being of a magneticmaterial, a permanent magnet stylus adapted to be moved over the otherof said windings to bring elements of the adjacent windings intointimate contact with each other, a source of potential, and associatedcircuitry for connecting the source to the windings to produce outputvoltages proportional to the coordinates of position of the stylus.

Thus, the principles of the present invention are directed to amagnetically-operated electrographic transmitter unit having a freestylus. The unit produces output voltages which can be transmitted to areceiver unit to control there the movements of another stylus orwriting instrument in correspondence with the movements of the freestylus at the transmitter. Alternatively, the output voltages providedby the unit can be applied to a long-persistency cathode ray tube toproduce on the face thereof a reproduction of the transmitted material.

gained from a consideration of the following detailed description inconjunction with the attached drawing, in which:

Fig. l is a perspective view of a magnetically-operated free styluselectrographic transmitter device illustrative of the principles of thepresent invention; and

Fig. 2 is a schematic representation of the transmitter device of Fig.1, and also includes a depiction of a switching assembly adapted to becombined therewith.

The structure shown in Fig. 1 includes a free stylus member 10, Le, astylus member having neither an electrical nor a mechanical connectionextending thereto. The member 10 may advantageously comprise a rodshapedpermanent magnet having an ink-holding bore 10a extending along the axisthereof and a ballpoint element 10b contained in a tapered end thereof.Thus, the stylus 10 may advantageously take the form of a ballpoint penthe tapered end of which concentrates the flux of the permanent magnetat the writing tip of the member 10.

Also shown in Fig. 1 is a sheet member 12 over each edge of which ispressed a slotted bar element. The bar elements 14, 15, 16 and 17 andthe sheet member 12 comprise the frame assembly of a transmitter deviceillustratively embodying the principles of this invention.

The noted components of the frame assembly may be made of an insulatingmaterial, or, alternatively, may be made of metal and then coated with asuitable insulating material.

The transmitter shown in Fig. 1 further includes lower and upperconductive windings 18 and 19, respectively. The lower winding or grid18 is of a magnetic material and is wound in tension over the'barelements 15 and 17, while the upper winding or grid 19 is of anon-magnetic material and is wound in tension over the bar elements 14and 16.

High tension is used in winding 19 so as to position each turn of thiswinding nearly rigidly in a common plane. A moderate tension is used inwinding 18, which permits each turn to be deflected when attracted bythe stylus and which suffices to restore it to its normal position whennot so attracted. The length of winding 18 is materially greater thanthe lengthwise dimension of the writing surface, in order to reduce thevariation in the force required to deflect this winding with variationwithin the length of the writing surface of the point deflected (i.e.,the location of the stylus).

The ends of the winding 13 are respectively connected to terminalmembers 20 and 21, and the ends of the winding 19 are respectivelyconnected to terminal members 22 and 23.

Advantageously, the windings 18 and 19 should lie in parallel planeswith a small separation between them. To aid in realizing thisobjective, leveling bars 25, 26, 27 and 28 are provided. The bars 26 and28 are positioned under the bottom winding 18, and the bars 25 and 27are positioned under the top winding 19. The leveling bars are securedto the sheet member 12 by screw elements the range of adjustment ofwhich allows the windings to be accurately positioned in closelyadjacent parallel planes.

The overlapping portion of the windings 18 and 19 defines the writingsurface of the transmitter unit. This surface may advantageously becovered by a thin sheet 24 of non-magnetic material of sufficientstiffness to form a firm surface when supported by the tensioned winding19.

One specific illustrative embodiment of the present invention includes amember 10 formed from a rod of permanently magnetizable material. Theembodiment further includes a sheet member 12 and bar elements 14,

15, 16 and 17 of aluminum, anodized and enameled to provide insulatingsurfaces. The bottom winding of the embodiment is of a high permeabilitylow retentivity magnetic material, and the top winding is of anon-magnetic material. The materials of the two windings 18 and 19-are'chosen so that the resistances of the windings are approximatelyequal.

In actual operation a sheet of paper 29 may advantageously be placedover the aforementioned non-magnetic sheet 24 so that an operator mayobserve what he is writing with the ballpoint stylus member 10.

Movement of the stylus over the above-described writing surface causeselements of the bottom or magnetic winding 18 to move into contactingrelationship with elements of the top ornon-magnetic winding 19, suchcontact being within a small region immediately below the location ofthe point of the stylus.

In rapidly moving a stylus member across the writing surface of anillustrative embodiment of the present invention, it is observed thateach attracted element of the bottom winding is subjected to a forcecomponent that tends to move the element in a direction transverse tothe desired direction of motion. In other words, an element may beattracted toward an adjacent wire of the same winding as well as towarda wire element of the also is shown one manner in which the device maybe connected to associated circuitry so that each point of contactbetween the lower and upper windings is translated into twocharacteristic voltages.

A direct current source 30, the negative terminal of which is grounded,has its positive terminal connected to an armature element 31a of aswitching relay which also includes armature elements 31b and 31c. Alead 34 connects a terminal 33 to the terminal 20 to which, as notedabove, one end of the bottom winding 18 is secured. The other end of thewinding 18 is secured to the terminal 21, and a lead 36 interconnectsthe terminal 21 and the armature element 310, which element 310 is shownin contact with a terminal 37. A lead extends from the terminal 37 toground, and another lead extends to a capacitor 40 and then to an outputterminal point 50 and another terminal point 48.

The contact that the free stylus member 10 effects between the windings18 and 19 is represented in Fig. 2 by a lead 41. The lead 41 is shown asthe link between two points 41a and 41b, the actual contact pointsbetween the windings 18 and 19, respectively.

One terminal 22 of the top winding 19 is connected by a lead 42 to thearmature clement 31b, which element 31b is shown in contact with aterminal 43. The terminal 43 is connected to an output terminal 60 andis also connected through a capacitor 44 to ground and a terminal 47.

With the switching relay in the position shown in Fig. 2, an outputvoltage appears from the output terminal 60 to ground. This voltage isproportional to the location of the contact point 41a in thepotentiometer 18, and hence to one coordinate (e.g., the x coordinate)of the position of the stylus 10.

When the relay is operated, the armatures 31a, 31b and 31c move intocontact with the terminals 46, 47 and 48, respectively. In this operatedposition, there appears I from the output terminal 50 to ground avoltage which is proportional to the location of the terminal 41b ofpotentiometer 19, and henceto the other coordinate (e.g.,

the y coordinate) of the stylus position. The charge on condenser 44maintains the voltage on terminal 60 at approximately the value it hadduring the preceding inter val. Thus, it is seen that in a giveninterval of time, determined by the switching rate of the relay, twooutput voltages corresponding to the coordinates of the position of thefree stylus 10 are provided by the hereindescribed electrographictransmitter. Advantageously, the switching rate of the relay is chosenso that good resolution of the transmitted material is obtained when thestylus is moved over the crossed sheets at high writing speeds.

The output terminals 50 and 60 may be connected by a transmission lineto a receiving device, including, inter alia, a long-persistency cathoderay tube. The impedances from the terminals 50 and 60 to ground shouldadvantageously be high compared to the impedances of the windings 19 and18, respectively.

It is, of course, to be understood that a number of other suitableswitching or circuit arrangements, either mechanical or electrical, maybe devised to replace the above-described switching means. For example,copending'application Serial No. 631,138, filed on December 28, 1956, inthe name of W. Koenig, Jr., discloses a circuit arrangement which mightbe combined with the herein-described magnetically-operated windings toproduce output voltages of the type desired. 7

The above-described embodiment of the present invention can be easilymodified in a number of ways by those skilled in the electromechanicalarts. For example, gold plating the windings 18 and 19 and encasing themin a dustproof container member are techniques well calculated toimprove the performance of the basic transmitter unit.

Also, it is to be understood that although a particular form of windingconstruction has been described and illustrated herein, any windingconfiguration that provides parallel adjacent elements may readily andsatis factorily be incorporated into an illustrative embodiment of thisinvention.

Additionally, it is to be understood that each of the crossed windingsof an illustrative embodiment of this invention may be of a magneticmaterial. Such an arrangement will not, however, usually be favored, forthe interposition of a magnetic winding between the stylus and theattracted or movable winding introduces a shielding effect that reducesthe attraction between the free stylus and the attracted winding to anappreciable extent. In view of this, emphasis herein has been placed ona transmitter device wherein one only of the windings is of a magneticmaterial.

Thus, the specifically described illustrative embodiment is amagnetically-operated free stylus transmitter device which is easilymanufactured and adjusted. Additionally, the device is easilymaintained, for it exhibits almost complete freedom from wearconditions. The only motion therein (aside from the motion of the stylusalong the writing surface) is the magnetically-induced elasticdeflection of the turns of the bottom winding.

It is to be understood that the above-described arrangements are onlyillustrative and not restrictive of the principles of the presentinvention. Other basic arrangements and modifications thereof may bedevised by those skilled in the art without departing from the spiritand scope of the invention. 1

What is claimed is:

1. An electrographic transmitter device comprising two crossed windingspositioned in closely adjacent parallel planes, one only of saidwindings being of a magnetic material, and a permanent magnet freestylus member, whereby elements of the magnetic winding. are attractedinto contacting relationship with elements of the nonmagnetic winding asthe stylus member is passed over that portion of the surface'of thenon-magnetic winding which overlaps the magnetic winding.

. 2. An electrographic transmitter device comprising two crossedwindings positioned in closely adjacent parallel planes, the lower ofsaid windings being of a magnetic material, a thin firm sheet ofnon-magnetic material positioned over the upper or non-magnetic winding,and a magnetized free stylus member adapted to be moved over theoverlapping portion of said non-magnetic sheet.

3. An electrographic transmitter device comprising two crossed windingspositioned in adjacent parallel planes, one only of said windings beingof a magnetic material, and a magnetized free stylus writing instrument,said instrument being adapted to be passed over the overlapping portionof the non-magnetic winding.

4. In combination, two crossed windings positioned in closely adjacentparallel planes, at least one of said windings being of a magneticmaterial, and permanently magnetized stylus means for attractingportions of the magnetic winding into contacting relationship withportions of the other winding.

5. In combination, two crossed windings positioned in adjacent parallelplanes, at least one of said windings being of a magnetic material,permanently magnetized writing means for attracting elements of themagnetic winding into contacting relationship with elements of the otherwinding, and circuit means for translating each point of contact betweensaid windings into characteristic voltages.

6. An electrographic transmitter comprising two windings arranged inparallel adjacent planes, one of said windings being of a magneticmaterial, a permanent magnet stylus adapted to be moved over the otherof said windings to bring elements of the adjacent windings intointimate contact with each other, a source of potential, and associatedcircuitry for connecting said source to said windings to producevoltages proportional to the coordinates of position of said stylus.

7. In combination, a rectangular insulated sheet, a slotted bar pressedover each edge surface of said sheet, a winding supported by each twoparallel bars, one only of said windings being of a magnetic material,the over lapping portion of said windings defining a writing surface,and permanently magnetized writing means for attracting elements of themagnetic winding into contacting relationship with elements of the otherwinding, whereby each different point of position of said writing meanson said writing surface causes contact between a different set of saidwinding elements.

8. Means for translating the movement of a magnetized stylus over aplane surface into voltages corresponding respectively to thecoordinates of successive locations of the stylus with respect to adatum point on said surface comprising crossed windings havingrespective plane portions of parallel conductors in spaced juxtapositionto each other and to the plane surface, the winding portion further fromsaid surface being of a magnetic material, whereby crosspoints of saidwindings are successively brought into mutual contact upon passage ofthe stylus over said surface, a power source, and means for connectingsaid source to said windings.

9. Means for translating the movement of a magnetized stylus over aplane surface into voltages corresponding respectively to thecoordinates of successive locations of the stylus with respect to adatum point on said surface comprising crossed plane grids, each gridincluding spaced parallel conductors, said grids being arranged inspaced parallel relation to each other and to said surface, theconductors of one grid being of magnetic material for attraction by thestylus into contact with the other grid at crosspoints of said gridscorresponding to the positions of the stylus, a power source, and meansfor connecting the source to said grids. I

References Cited in the file of this patent FOREIGN PATENTS

